The modern downhill ski boot is meant to rigidly attach flat against the ski surface, so as to provide the wearer with as much control over the ski as possible. Skis and ski boots, while coupled together, essentially act as a single, rigid unit, transferring torques and forces from the point of contact with the earth to the wearer's legs, feet, and ankles.
With this aim in mind, a ski boot is also as rigid as possible, so as to prevent the user's foot from flexing, turning side to side, rocking front to back, or rolling side to side. Further, the ski boot is meant to keep the ankle and foot in a set, acute angle with respect to each other. This is because skiing is best performed with bent knees; bending the knees forces the ankles and feet into an acute angle.
These mechanics are inherently incompatible with the basic mechanics of walking. With each normal walking stride, the feet flex and rock front to back, and the ankle joint flexes freely, allowing the foot-to-ankle angle to change continually through the stride. As such, ski boots perform their skiing task well, but are ill designed for walking. Walking about in ski area parking lots, stairs, ski lodges, sidewalks, and apres-ski snackbars and lounges is a difficult, loud, uncomfortable, and even comic affair.
Further, walking on hard surfaces with ski boots damages the soles of the boots, which are usually made of a rigid plastic, and which can ultimately lead to the need to replace the boots.
Taking the boots off for walking is often not an option because regular footwear is stored away in lockers or left in automobiles. Moreover, taking the boots on and off is cumbersome and time consuming, and it is heavy to carry the boots, and so users often forgo this option.
Many have attempted to overcome this problem using various designs of ski boot soles or ski boot sole attachments. The most common invention in the prior art utilizes a bulky, attached curved or angled lower walking surface that essentially allows the boot to rock back to front over the curved or angled surface. (See, e.g., Groves '602, Booty '397, Calkin '104, Bunke '504.)
Another approach has been to alter the sole of the ski boots themselves, to provide for a more natural walking gait, once again using curved or angled surfaces, which, in this case, are fixed onto the bottom of the ski boot. (See, e.g., Brugger-Stuker '144, Weninger '179, Kastinger '309.) With this second general approach, typically, the boot's sole is mechanically repositioned and the walking surface on the bottom of the boot is physically altered by the user, once the boot is unattached from the ski. Various methods have included flipping a hinged piece down under the boot sole, or moving the boot's sole into a new position.
An inherent problem in the prior art of using attachments or these alterations to ski boots themselves is that the attachments and alterations are bulky because of their curved or angled nature. Curved pieces take up extra room and can make use unnecessarily complicated. Separate curved attachments are hard to stack together, do not stack flat, and take up more room in a backpack or bag.
Another inherent problem in the prior art mentioned above is weight. The materials needed to construct a rigid undersole can be heavy, adding weight to already heavy ski boots and making carrying of the undersoles difficult when not in use. Once again, this added weight makes carrying attachments in a backpack or bag uncomfortable and undesirable.
Similarly, by their rigid nature, curved attachments are more cumbersome to carry than attachments that are flexible and relatively soft. A few have taken the approach of a soft, flexible undersole attachment, such as Koniuk '059 and Kelz '578, but these approaches have their own inherent limitations as well. Kelz '578, in particular, is only designed to help with traction, not the walking motion; they provide no assistance with the motion of walking. The attachment in Koniuk '059, while softer than the prior approaches, sacrifices traction through the use of a curved attachment and adds the problems of bulk mentioned above.
Moreover, the prior art is replete with overly complicated attachment methods, such as front and rear clips. (See, e.g., Frey '880.)
The invented apparatus solves the problems inherent in the prior art, as summarized below.